its either the shift rod or the gear synchro in the tranny which almost never goes out try adjust your shift by loosening the bolts to the stick then putting the car in nd gear and re tightening them if youre still having trouble loosen an put into th gear then tighten also check your shift rod bushing it is in the cavity under the shift stick and it adds rigidness to the shift if youre still having problems check the integrity of the transmission mounts before looking into another tranny